Hero of Alexandria

Heron of Alexandria (Greek: Ἥρων ὁ Ἀλεξανδρεύς, Heron ho Alexandreus; also known as Hero of Alexandria c. 10 AD – c. 70 AD) was a Greekmathematician and engineer who was active in his native city of Alexandria, Roman Egypt. He is considered the greatest experimenter of antiquity[1] and his work is representative of the Hellenistic scientific tradition.[2]

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It is almost certain that Heron taught at the Musaeum which included the famous Library of Alexandria, because most of his writings appear as lecture notes for courses in mathematics, mechanics, physics, and pneumatics. Although the field was not formalized until the twentieth century, it is thought that the work of Heron, his automated devices in particular, represents some of the first formal research into cybernetics.[5]

Heron described[6] the construction of the aeolipile (a version of which is known as Heron's engine) which was a rocket-like reaction engine and the first-recorded steam engine (although Vitruvius mentioned the aeolipile in De Architectura some 100 years earlier than Hero). It was created almost two millennia before the industrial revolution. Another engine used air from a closed chamber heated by an altar fire to displace water from a sealed vessel; the water was collected and its weight, pulling on a rope, opened temple doors.[7] Some historians have conflated the two inventions to assert that the aeolipile was capable of useful work.[8]

The first vending machine was also one of his constructions; when a coin was introduced via a slot on the top of the machine, a set amount of holy water was dispensed. This was included in his list of inventions in his book Mechanics and Optics. When the coin was deposited, it fell upon a pan attached to a lever. The lever opened up a valve which let some water flow out. The pan continued to tilt with the weight of the coin until it fell off, at which point a counter-weight would snap the lever back up and turn off the valve.[9]

A windwheel operating an organ, marking the first instance of wind powering a machine in history.[3][4]

Hero also invented many mechanisms for the Greek theater, including an entirely mechanical play almost ten minutes in length, powered by a binary-like system of ropes, knots, and simple machines operated by a rotating cylindrical cogwheel. The sound of thunder was produced by the mechanically-timed dropping of metal balls onto a hidden drum.

The force pump was widely used in the Roman world, and one application was in a fire-engine.

A syringe-like device was described by Hero to control the delivery of air or liquids.[10]

In optics, Hero formulated the principle of the shortest path of light: If a ray of light propagates from point A to point B within the same medium, the path-length followed is the shortest possible. It was nearly 1000 years later that Alhacen expanded the principle to both reflection and refraction, and the principle was later stated in this form by Pierre de Fermat in 1662; the most modern form is that the path is at an extremum.

Automata, a description of machines which enable wonders in temples by mechanical or pneumatical means (e.g. automatic opening or closing of temple doors, statues that pour wine, etc.); See Automaton and Bernardino Baldi's translation[15]

Mechanica, preserved only in Arabic, written for architects, containing means to lift heavy objects

Metrica, a description of how to calculate surfaces and volumes of diverse objects

On the Dioptra, a collection of methods to measure lengths, a work in which the odometer and the dioptra, an apparatus which resembles the theodolite, are described

^For example: Mokyr, Joel (2001). Twenty-five centuries of technological change. London: Routledge. p. 11. ISBN0-415-26931-8. Among the devices credited to Hero are the aeolipile, a working steam engine used to open temple doors and Wood, Chris M.; McDonald, D. Gordon (1997). "History of propulsion devices and turbo machines". Global Warming. Cambridge, England: Cambridge University Press. p. 3. ISBN0-521-49532-6. Two exhaust nozzles...were used to direct the steam with high velocity and rotate the sphere...By attaching ropes to the axial shaft Heron used the developed power to perform tasks such as opening temple doors

^Humphrey, John W.; John P. Oleson; Andrew N. Sherwood (1998). Greek and Roman technology: A Sourcebook. Annotated translations of Greek and Latin texts and documents. Routledge Sourcebooks for the Ancient World. London and New York: Routledge. ISBN978-0-415-06137-7., pp. 66–67